How to call a non-static method?

Question

C++ / C#

There is a code:

static async void Bot_OnMessage(object sender, MessageEventArgs e)
        {
            Head hd = new Head();
            if (e.Message.Text != null && e.Message.Chat.Id == myChatId)
            {
                
                await botClient.SendTextMessageAsync(
                  chatId: myChatId,
                  text: "You said:\n" + e.Message.Text
                );
                hd.writeLog("sdgergergreg");
            }
        }
public void writeLog(string text)
    {
        logText.Text = logText.Text + DateTime.Now +  text // + "\n";
    }

hd.writeLog("sdgergergreg"); - here he should add "sdgergergreg" to the TextBox, but nothing is added there.